Re: [Xen-users] Consistent snapshots

[John Haxby <john.haxby@xxxxxxxxxx>]

On 25/06/09 11:01, Gak wrote:
> How do i create consistent snapshots of VM's from Dom0?. What are the 
> backup methods or snapshot/snaprestore methods that are followed for 
> Xen Virtual environments?.
Shut down the VM, take the snapshot.

Anything else requires serious cooperation from VM and, equally 
importantly, the applications running in it.  Sometimes you can get away 
with suspending the guest and taking a snapshot of memory and disk at 
the same time -- that isn't very useful though because to recover, say, 
an individual file from the back up you have to restart the suspended 
copy.  Even worse, if there are any in-flight transactions between the 
VM and other machines (virtual or otherwise) those will restart -- 
having your bank balance debited twice would be very annoying.
In the general case, you're better off running your backup within the 
VM.  In special cases you can do something different -- for example, you 
might have a database that can get itself into a consistent state so you 
can take a snapshot of its file system on a suitable NAS or SAN.
jch

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